1. Field of the Invention
The present invention relates to a method of manufacturing an ink jet recording head, and, more particularly, to a selected transfer-molding resin composition suitable to manufacture a recording head by utilizing a transfer molding method, and to an ink jet recording head manufactured by using the aforesaid resin composition.
2. Related Background Art
An ink jet recording head (hereinafter called a "recording head") for use in an ink jet recording method ordinarily has ink discharge ports from which ink is discharged, a fluid chamber for storing ink to be supplied to the discharge ports, a fluid passage which connects the discharge ports and the fluid chamber to one another, energy generating devices disposed in a portion of the fluid passage and arranged to discharge energy for discharging ink, and an ink supply port through which ink is supplied to the fluid chamber from outside.
The conventional recording head has been manufactured anyone of the following methods.
(1) A method in which a first substrate having energy generating devices disposd thereon is used, recesses to be utilized to form the ink discharge ports, the fluid passage and the fluid chamber, and the ink supply port to connect the fluid chamber and the outside to each other are respectively formed in a second substrate made of glass or metal by machining means such as cutting or etching, and then the first and the second substrate are bonded to each other with an adhesive while aligning the energy generating devices and the fluid passage with each other.
(2) A method in which a positive-type or a negative-type photosensitive dry film is applied to a first substrate having energy generating devices formed thereon and made of glass or the like, the pattern of the photosensitive dry film corresponding to the ink discharge ports, the fluid passage and the fluid chamber is masked or allowed to appear outside so as to be exposed to light, and is developed so that a solid layer of the pattern corresponding to the discharge ports, the fluid passage and the fluid chamber is formed on the first substrate. A liquid hardening material, to which a hardening agent is mixed, is applied to the solid layer and to the first substrate to have a proper thickness, and the first substrate is allowed to stand at a predetermined temperature for a long time so that the hardening material is hardened. Then, the first substrate on which the hardening material has been hardened, is cut at a position at which the ink discharge port will be formed, and the end surface of the solid layer is allowed to appear outside, and the first substrate is dipped in a solution which dissolves the solid layer so that the solid layer is dissolved and removed from the first substrate, on which the hardening material has been hardened, and spaces for forming the fluid passage and the fluid chamber are formed (refer to Japanese Patent Application Laid-Open No. 61-15497).
(3) A method in which a positive-type or a negative-type photosensitive dry film is applied to a first substrate having energy generating devices thereon, the pattern of the photosensitive dry film corresponding to the ink discharge ports, the fluid passage and the fluid chamber is masked or allowed to appear outside so as to be exposed to light, and is developed so that the solid layer of the pattern corresponding to the discharge ports, the fluid passage and the fluid chamber is formed on the first substrate. An active-energy-ray hardening material, which is hardened by active energy rays, is applied to the solid layer and the first substrate to have a proper thickness, a second substrate through which the active energy rays are able to transmit and which has a recess for forming a portion of the fluid chamber and the ink supply port are formed is bonded on the active energy ray hardening material while aligning the recess to the position at which the fluid chamber will be formed so that a stacked member is formed. Then, the second substrate is masked in such a manner that a portion of the active energy ray hardening material, in which the liquid chamber will be formed, is covered so as to irradiate the active energy ray hardening material with the active energy rays through the second substrate so that the active energy ray hardening material is hardened. Then, the stacked member, on which the active energy ray hardening material has been hardened, is cut at a position at which the ink discharge port will be formed, and the end surface of the solid layer is allowed to appear outside, and the stacked member is dipped in a solution which dissolves the solid layer and the non-hardened active energy ray hardening material so that the solid layer and the non-hardened active energy hardening material are dissolved and removed from the stacked member, and spaces for forming the fluid passage and the fluid chamber are formed (refer to Japanese Patent Application Laid-Open No. 62-253457).
(4) A transfer molding manufacturing method has been disclosed recently which is arranged in such a manner that a molding resin is injected into a mold having cavities and projections for forming the fluid passage, the fluid chamber, the ink supply port and the ceiling board, and the molding resin ms hardened and molded at a predetermined injection pressure and molding temperature. After the resin has been molded, the discharge surface is cut and ground if necessary, and the solid layer is dissolved and removed by a proper solvent so that the ink chamber including the ink supply port, the fluid passage and the ink discharge port are formed.
The transfer molding method (4) of the aforesaid conventional methods of manufacturing a recording head enables the process for precisely aligning the two substrates and bonding them to each other to be eliminated. Therefore, precise, reliable, and low cost ink jet recording heads, which can easily be mass-produced, can be manufactured by simple processes while decreasing the number of the processes. However, the manufactured recording head sometimes encounters a defect because thermal stress generated in the recording head at the time of the transfer molding process due to the contraction of the resin at the time of hardening and due to the difference in the expansion coefficient between the resin and the substrate causes the substrate to be broken at the time of the cutting process performed for the purpose of forming the discharge port and causes the resin and the substrate to be separated from each other. If the recording head is allowed to stand in a high temperature and high humidity condition for a long time, the interface between the resin and the substrate can be separated. It can be considered that the reason for this lies in that the adhesion between the resin and the substrate deteriorates due to the thermal stress generated at the time of manufacturing the recording head and due to the ink resistance of the resin. If the separate takes place in the interface between the resin and the substrate, pressure waves propagate to the adjacent nozzle while affecting the ink discharge.